Water cooled exhaust tube

ABSTRACT

Combustion engine (M), especially an Otto engine or diesel engine for land and water vehicles, has an exhaust system with an exhaust catalyst ( 20 ), integrated in the exhaust pipe (L), and a catalyst cooling device ( 26 ) fed with a fluid or pasty coolant ( 14 ), preferably water, glycerin or a gel. Also claimed is a silencer, especially for the above combustion engine, having a silencer cooling device fed with a fluid or pasty coolant. Preferably, the cooling device ( 26 ) forms a housing (G) for the catalyst ( 20 ) or silencer, respectively.

The present invention relates to an exhaust tube for conducting exhaustgases from a combustion engine, at which the exhaust gases are cooled bymeans of water. Primarily, but not exclusively, the invention concernsexhaust tubes from boat engines.

In order to prevent the exhaust tube from a boat engine from becoming sohot that big difficulties arise concerning its placement in the boat, itis desirable to cool the exhaust gases. A commonly used known way to dothis is to inject water into the exhaust tube a short distancedownstream of the engine. Depending on how this injection is doneseveral problems arise.

On boats the exhaust outlet is often located at the stern, or on a sideof the boat hull, whereby the outlet is located relatively low. A reasonfor this that the outlet has to be placed lower than the engine, or atleast the exhaust thereof, in order to prevent cooling water, injectedinto the exhaust tube to cool the exhaust gases, from being forced bygravity back into the engine, which would be the case if the outlet islocated higher than the engine.

A problem often occurring on boats having the exhaust outlet located atthe stern or on a side of the boat hull is that during engine operationexhaust gases discharged from the outlet often temporarily remain in theregion around the outlet, and can cause discomfort and even be unhealthyfor passengers on the boat. In particular a problem arises on a boatwith the exhaust outlet on the stern. When the boat is in engine poweredmotion the airflow around the boat often presents a wake at the stern.This can cause exhaust gases to remain at the stern and even spread upon the aft part of the deck.

The object of the invention is to present an exhaust tube, which avoidsthese problems, but has an acceptably low temperature. According to theinvention this is accomplished with an exhaust tube presenting thecharacterizing features in claim 1.

Thus, a channel is formed between the housing and the inner tube,conducting the cooling water separately from the exhaust gases, flowingthrough the inner tube. The dimensions of the channel and the flow ofthe cooling water are adapted to the temperature of the exhaust gasesand the material in the housing and the inner tube, so that the externaltemperature of the housing obtains an acceptably low level duringoperation.

Preferably, a channel having a screw line shape wrapping the inner tubeis provided between the inner tube and the housing. This provides forsecuring that high regions of the cross-section of the exhaust tube isprovided with cooling water as well as low regions thereof.

The construction allows for the housing as well as the inner tube to bemade flexible, and for either one, preferably both of them, is made inrubber. Thus, the inner tube can constitute a rubber hose.

Having the inner tube, the outer housing and the cam made in a flexiblematerial allows for the installation of the exhaust tube in itsenvironment, for example a boat, to be done in a much simpler way thanwhat would be the case with a non-flexible material. Allowing theexhaust tube to flex when installed eliminates the need for adapting thelength of exhaust tube sections to relatively close tolerances.Additionally, tube bending and other installation preparation taskswould be eliminated.

Tests have shown that arranging the exhaust tube with a water jacketaround the inner tube and using rubber material for the exhaust tubeprovides excellent sound dampening qualities. A water jacketed exhausttube using metal such, as stainless steel, for the inner tube andhousing provides some silencing effect compared to a single tube exhaustpipe, according to known art, but the silencing quality is greatlyreinforced, if the water jacket is combined with a flexible material forthe exhaust tube.

The inner tube is affected by the hot exhaust gases. According to apreferred embodiment of the invention, the inner tube is arranged to bereplaceable in the housing. This means that it can be made out of acheap material and be replaced when needed, without the outer housingand the cam having to be replaced at the same time.

In an embodiment of the exhaust tube, especially suitable for boats, thecam is made in rubber integrated with the housing on the interior of thewall of the housing. Thereby, the outer housing and the cam can bemanufactured as one unit. Alternatively, the cam can be formed as aseparate element. The cam can also be formed on the exterior of theinner tube. An inner tube and a cam integrated on its exterior providesfor a unit which greatly facilitates a rubber manufacturing processthereof.

According to a further development of the invention the exhaust tube canbe carried out as a silencer. The silencer can be included as a shortersection, formed with a larger diameter, of a longer exhaust tubeaccording to the invention, or be connected to an exhaust tube ofanother kind. A big advantage with such a silencer is that anuninterrupted cooling water flow is obtained, i.e. the cooling waterflow from the exhaust tube located upstream of the silencer continuesaround the silencer and onward downstream of the latter. This means thatthe silencer becomes cooler, and no separate conduits are required forthe cooling water.

Since the silencer water-jacketed the silencing becomes very effective,especially if all components included are made in rubber. However, asmentioned above, the rest of the exhaust tube has, without any specialsound dampening means in it, a sound dampening effect, especially whenformed entirely in rubber.

For boats and other installations, in which the exhaust tube has anessentially horizontal orientation, the screw line shaped cooling waterchannel is advantageous, since it forces the water to flow throughelevated parts of the exhaust tube, so that no parts of the exterior ofthe inner tube end up having no cooling. However, even if the exhausttube according to the invention has special advantages in boats, theinvention is not limited to these, rather it can be applied, e.g. insmall stationary or mobile set-ups with a combustion engine, such ascompressors or reserve power stations, at which the exhaust tubepossibly partly can be in the form of a vertical chimney.

In the description and in the claims, the expression “rubber” shall beunderstood in a wide sense and be regarded to comprise also other highlyelastic, materials similar to rubber apart from rubber. For differenttypes of usable materials similar to rubber we refer to, e.g. Ullman,Encyclopedia of Industrial Chemistry, Fifth Completely Revised Edition,pp 242-243.

The invention will be described closer below with reference to theaccompanying drawing, in which

FIG. 1 shows a longitudinal cross-section through a part of an exhausttube according to one embodiment of the invention,

FIG. 2 shows schematically a sectioned part of an exhaust tube with asilencer section according to another embodiment of the invention,

FIG. 3 shows schematically a partially sectioned part of an exhaust tubewith a silencer section according to yet another embodiment of theinvention,

FIG. 4 shows schematically a partially sectioned part of an exhaust tubewith a silencer section according to a further embodiment of theinvention,

FIG. 5 shows a boat equipped with an exhaust tube according to anadditional embodiment of the invention,

FIG. 6 shows a part of the exhaust tube according to the additionalembodiment of the invention,

FIG. 7 shows a cross-section of the exhaust tube according to theadditional embodiment of the invention, the cross-section being locatedat the line VII—VII, and

FIG. 8 shows a view of the exhaust tube according to the additionalembodiment of the invention, sectioned along the line VIII—VIII in FIG.6.

The exhaust tube shown in cross-section in FIG. 1 is manufacturedentirely in rubber and is constituted by an inner tube 1 in the form ofa hose, as well as an outer housing 3, surrounding the inner tube. Boththe rubber hose 1 and the housing 3 are circularly cylindrical andmutually arranged coaxially. A cam 7 is arranged on the interior of thewall 5 of the housing 3, which cam extends substantially in aperpendicular angle to the wall 5 and radially towards the inner tube 1.The cam has a rounded top 9 and the height of the cam from the wall 5corresponds substantially to half the difference between the innerdiameter if the housing wall 5 and the outer diameter if the inner tube1. Additionally, the cam 7 extends in a screw line shaped manner alongthe exhaust tube in the space between the inner tube 1 and the housing3. The top 9 of the cam 7 forms a ridge, which, along a screw line,sealingly abuts the exterior of the inner tube 1. Thereby, a screw lineshaped channel 11 is formed in this space.

The cam 7 can also be integrated with the inner tube and located on theexterior thereof. In this case also, the cam could have a ridge on thetop 9 for sealing abutment against the interior of the housing.

According to an alternative, more than one cam 7, preferably three cams,can be provided between the inner tube and the housing, in turn creatinga corresponding number of channels 11. Also, the cam, or cams could,instead of presenting a screw line shape, extend straight in the axialdirection of the exhaust tube. Multiple channels 11 provides forsecuring that high regions of the cross-section of the exhaust tube areprovided with cooling water as well as low regions thereof.

As a further alternative, the cam 7, or cams, could be divided intoaxially separated sections, to form guides for the water flow alonglimited sections of the exhaust tube. In a special version of thisalternative the cams would take the form of blades, each of which exertsa force upon the flowing water, causing it to rotate. Combined with theintegration of the blades on either the inner tube or the housing, thiswould lead to less friction when the inner tube and the housing aremoved in relation to each other during assembly or disassemblyoperations of the exhaust tube.

When installed, the inner tube 1 is connected is a suitable way, notshown, to the exhaust outlet of the engine. The exhaust gases flowthrough the inner tube 1 in the direction of the arrow A. The other endof the inner tube 1 can be connected to another exhaust tube, a silenceror, in a boat, emerge through the stern of the boat. Cooling water isconducted into the channel 11 at one end of the inner tube 1, shown inFIG. 1 by the arrow B. The cooling water then flows in a screw lineshaped manner in the channel 11 around the inner tube 1 and along thelatter in the same longitudinal direction as the exhaust flow A, to bedischarged at last, in a manner not shown, from the exhaust tube atanother place, here indicated with the arrow C.

I FIG. 2 a further development of the invention is shown, in which theexhaust tube within a limited longitudinal section 13 forms a silencer.Within the section 13 the housing 3 as well as the inner tube 1 areformed with a larger diameter than elsewhere in the exhaust tube.Thereby, the inner tube 1 forms a cylindrical chamber 15, but this aswell is surrounded at a distance by the outer housing 3 and the cam 7,which extends in a screw line shaped manner in the space between thehousing and the inner tube. Within the chamber 15 silencing means arearranged. These could be of a conventional known type, for exampledivision walls provided with holes, or, as indicated in FIG. 2, afilling material adapted to let gases pass or a porous mass 17.

Suitably, in the silencer section 13 all components, the inner tube 1,the cam 7 as well as the housing 3, are made in rubber. However, forcertain applications it can be advantageous to combine components indifferent materials, or to make all components in a material differentthan rubber, e.g. steel. For example, a cylindrical silencer with asingle steel jacket can be covered with an outer housing in rubber,having a screw line shaped cam on the inside. The important thing isthat a water jacket with a screw line shaped cooling water channel iscreated, by which sound dampening as well as cooling is obtained.

FIG. 2 shows that the axial ends of the longitudinal section 13 are madewith the same diameters as the rest of the exhaust tube. The joining ofthe section 13 to the rest of the parts of the exhaust tube can be donein a suitable way. For example, a sleeve coupling 19 in metal, e.g.stainless steel, be arranged inside the inner tube 1. The diameter ofthe sleeve coupling 19 is selected so that an inner tube 1 in rubber canbe struggled onto the sleeve coupling and remain on the sleeve couplingby its elastic force. In a corresponding manner, the end of the outerhousing 3 can be struggled onto a sleeve coupling 21 situated therein.This is shown in the right part of FIG. 2. The left part of FIG. 2 showsa corresponding joint, at which, however, tube clamps 23 are arranged onthe exterior of the housing 3, above the sleeve coupling 21 toaccomplish a stronger connection. If so desired, tube clamps can also bearranged around the inner tube 1 to clamp the latter against the sleevecoupling 19.

Joints corresponding to the ones showed in FIG. 2 can also be used tojoin to evenly thick sections of the exhaust tube. Hereby, a change toanother material can be done for the inner tube 1, the housing 3 orboth. For example, close to the engine, the inner tube 1 can be made ofa metal braid, but at a distance from the engine it can be joined with acheaper, simple rubber hose.

FIG. 3 shows a part of an exhaust tube with a silencer section accordingto yet another embodiment of the invention. Here a silencing means 17,extends in essentially the same direction as an inner tube 1 of theexhaust tube. Additionally, it has a similar cross-section as the innertube 1. It could be of a conventional known type, i.e. a fillingmaterial adapted to let gases pass, a porous mass, or presenting withdivision walls provided with holes.

This means that an outer housing 3, delimiting a channel for conductingcooling water, can extend throughout the part of the exhaust tubepresenting the silencing means with a constant cross-section. Also, acam 7 can be used as described above, at which the “screw” formed by thecam 7 will have a constant diameter throughout if part with thesilencing means. This will allow for a silencer with a simple design,having fewer parts than silencers according to known art, and in turn,will be cheap in production.

In FIG. 3, the inner tube 1 is discontinued at the silencing means 17,at which the inner tube is joined to the silencing means 17 byoverlapping the silencing means at the ends of the latter. A press fitcan provide a mounting force between the silencing means and the innertube. Alternatively, a hose clamp can be used to secure the inner tube 1to the ends of the silencing means 17. As a further alternative theinner tube 1 can extend pass the entire silencing means 17, or a part ofthe latter.

In FIG. 3, the housing 3 is divided at the silencing means 17, at whichtwo ends of the housing 3 are joined by means of a sleeve coupling 19,similar to the one described above with reference to FIG. 2.

FIG. 4 shows an alternative to the embodiment shown in FIG. 3. Here aouter housing 3 extends uninterrupted along a section of the exhausttube containing a silencing means 17, similar to the one described withreference to FIG. 3. Additionally, a cam 7 also extends uninterruptedlypass the silencing means 17. This provides for a very simpleconstruction, at which no special parts are needed for the housing 3 andthe cam 7 at the silencing means 17. Also, assembly of the exhaust tubewill be very easy, since the housing 3 and the cam 7 can be placed overthe silencing means in the same manner as they would over any other partof the inner tube 1. The arrangement shown in FIG. 4 also makesmaintenance and replacement of the silencing means easy.

Although the exhaust tubes in the embodiments described above presentcircular cross-sections, other cross-sectional shapes can be used, e.g.square, rectangular etc. Additionally, instead of being coaxial theinner tube 1 can be located off-center in the housing 3.

FIG. 5 shows a power boat 31. The exhausts from an engine in the boat 31are conducted through an exhaust tube 32 having in an essentiallyvertical orientation. The exhaust tube 32 is adapted to conduct exhaustgases upwards towards an outlet 33 at the top. The outlet 33 is locatedabove the hull and deckhouse of the boat, and also above any passenger.Thereby the exhausts are discharged in air moving in relation to theboat, during operation of the latter, and also at a distance from thepassengers.

The exhaust tube 32 comprises an inner tube 34, shown in cross-sectionin FIG. 7, adapted to guide the exhaust gases. At an upper end of theinner tube 34 the outlet 33 is formed. An outer housing 35 surrounds theinner tube 34. In FIG. 7 the inner tube and the housing have rectangularcross-sections, but alternative cross-sections can be used, e.g.circular, elliptical, square, or other. Also the inner tube 34 and thehousing 35 can present mutually differently shaped cross-sections.

In FIG. 7 the inner tube 34 is oriented coaxially to the housing 35 andan inner face 36 of the housing is located at a distance from an outerface 37 of the inner tube 34, whereby a cooling channel 38 is formed.The cooling channel 38 extends along the inner tube 34 and around thelatter. It is adapted to conduct cooling water for cooling the exhausttube. An alternative arrangement could comprise more than one coolingchannel distributed around the inner tube and separated by walls orcams.

Referring to FIG. 8, the cooling channel 38 communicates with a waterpump (not shown), which is adapted to pump water upwards through thecooling channel 38. At an upper end of the cooling channel an end wall39 is located. The inner tube 34 extends through the end wall 39.Alternatively, the outlet 33 is located by the end wall 39.

A return channel 40, shown in FIGS. 7 and 8, extends in the samedirection as the rest of the exhaust tube 32. I is located on one sideof the housing 35. The return channel 40 is at its top end delimited bythe end wall 39, and communicates at a low region with the water pump.As can be seen in FIG. 8, the cooling channel 38 and the return channel40 communicate via an opening 41 at the respective top ends of thechannels 38, 40. Water is pumped, by means of the water pump, upward inthe cooling channel 38. When the water reaches the top of the coolingchannel 38 it passes through the opening 41 and is gravity fed downwardin the return channel 40. Alternatively, water can be pumped upwards inthe return channel 40 and conducted downwards in the cooling channel.

The cooling channel 38 could communicate with a screw line shapedchannel 11 of a portion of the exhaust tube, similar to the onedescribed above with reference to FIG. 1. The material for the exhausttube in FIGS. 5-8 can the any suitable material, such as stainlesssteel. Alternatively, a flexible material, such as rubber can be used,to allow for the exhaust tube to be more easily installed in a variationof environments.

As an alternative, the inner tube 34 does not have to be coaxial withthe outer housing 35, but can have a cross-section with a center locatedapart from the center of the cross-section of the housing 35.

An additional feature of the exhaust tube in FIGS. 5-8 can be a cam 7similar to what has been described above with reference to FIG. 1. Thecam would extend in a spiral shaped manner along the exhaust tube, andspan between the inner tube 34 and the housing 35. The cam would secure,especially in a case where the exhaust tube is oriented in an angle fromthe vertical direction, that all sides of the exhaust tube would beprovided with cooling water.

The arrangement described with reference to FIGS. 5-8 allows for anexhaust tube for water cooled exhaust gases to be oriented so that theoutlet is located above the engine. The water jacket provided around theinner tube provides for the external temperature of the exhaust tube tobe considerably lower than in a conventional exhaust tube. This meansthat temperature of the outer face of the exhaust tube can be low enoughfor the latter to be extended through areas where it otherwise wouldhave caused heat problems for materials, structures and persons.

With the described arrangement the exhaust tube can be located, e.g. onthe deck of a boat without causing the risk of persons on deck to burnthemselves on the exhaust tube. The exhaust tube can also be extendedthrough an internal space of the boat, which space could be intended forpassengers, without causing the risk of these passengers to burnthemselves or for any interior or loose parts to catch fire.Additionally, the exhaust tube can be integrated in a structure on thetop of the boat, such as a stand for antennas and lanterns, or a riggingfor sails, without causing heating problems for the structure.

1. An exhaust tube for conducting exhaust gases from a combustionengine, whereby the exhaust gases are cooled by means of water, whereinthe exhaust tube comprises an outer housing formed as a tube, and aninner tube extending at a radial distance from the housing, the innertube being adapted to conduct the exhaust gases while at least onechannel, formed between the housing and the inner tube, is adapted toconduct cooling water separately from the exhaust gases, the inner tubeextending coaxially in the housing, the exhaust tube comprising at leastone cam, spanning the distance between the housing and the inner tube,the cam extending in a screw line shaped manner in the longitudinaldirection of the housing, whereby the channel extends in a screw lineshaped manner between the housing and the inner tube.
 2. An exhaust tubeaccording to claim 1, wherein the cam is arranged on the interior of thewall of the housing, the cam being made in rubber, the top of the cam,in a cross-sectional view, being rounded to form a ridge for a sealingabutment against the exterior of the inner tube.
 3. An exhaust tubeaccording to claim 2, wherein the inner tube is replaceable in thehousing.
 4. An exhaust tube according to claim 1, wherein the cam isarranged on the exterior of the wall of the inner tube, the cam beingmade in rubber, and the top of the cam, in a cross-sectional view, beingrounded to form a ridge for a sealing abutment against the interior ofthe housing.
 5. An exhaust tube according to claim 4, wherein the innertube is replaceable in the housing.
 6. An exhaust tube for conductingexhaust gases from a combustion engine, whereby the exhaust gases arecooled by means of water, wherein the exhaust tube comprises an outerhousing formed as a tube, and an inner tube extending at a radialdistance from the housing, the inner tube being adapted to conduct theexhaust gases while at least one channel, formed between the housing andthe inner tube, is adapted to conduct cooling water separately from theexhaust gases, the inner tube extending coaxially in the housing, theexhaust tube comprising a plurality of cams, spanning the distancebetween the housing and the inner tube, the cams extending straight inthe axial direction of the exhaust tube.
 7. An exhaust tube forconducting exhaust gases from a combustion engine, whereby the exhaustgases are cooled by means of water, wherein the exhaust tube comprisesan outer housing formed as a tube, and an inner tube extending at aradial distance from the housing, the inner tube being adapted toconduct the exhaust gases while at least one channel, formed between thehousing and the inner tube, is adapted to conduct cooling waterseparately from the exhaust gases, the exhaust tube comprising at leastone cam, spanning the distance between the housing and the inner tube,the cam extending in a screw line shaped manner in the longitudinaldirection of the housing, whereby the channel extends in a screw lineshaped manner between the housing and the inner tube, in addition towhich the housing and the inner tube are flexible.
 8. An exhaust tubeaccording to claim 7, wherein the inner tube is made in rubber, inparticular a rubber hose.
 9. An exhaust tube according to claim 7 or 8,wherein the housing is made in rubber.
 10. An exhaust tube forconducting exhaust gases from a combustion engine, whereby the exhaustgases are cooled by means of water, wherein the exhaust tube comprisesan outer housing formed as a tube, and an inner tube extending at aradial distance from the housing, the inner tube being adapted toconduct the exhaust gases while at least one channel, formed between thehousing and the inner tube, is adapted to conduct cooling waterseparately from the exhaust gases, the inner tube extending coaxially inthe housing, the exhaust tube comprising at least one cam, spanning thedistance between the housing and the inner tube, the cam extending in ascrew line shaped manner in the longitudinal direction of the housing,whereby the channel extends in a screw line shaped manner between thehousing and the inner tube, in addition to which silencing means arearranged in the inner tube.
 11. An exhaust tube according to claim 10,wherein the screw formed by the cam has a constant diameter throughoutan exhaust tube part including the silencing means.
 12. An exhaust tubefor conducting exhaust gases from a combustion engine, whereby theexhaust gases are cooled by means of water, wherein the exhaust tubecomprises an outer housing formed as a tube, and an inner tube extendingat a radial distance from the housing, the inner tube being adapted toconduct the exhaust gases while at least one cooling channel, formedbetween the housing and the inner tube, is adapted to conduct coolingwater separately from the exhaust gases, the exhaust tube being adaptedto be mounted in a water-vessel, to extend from a first region to asecond region of the latter, the second region being located higher thanthe first region, whereby the housing delimits the at least one coolingchannel surrounding the inner tube, whereby water pump means areprovided to pump water for it to flow through the cooling channel,wherein the outlet of the exhaust tube is located above or at a top endof the cooling channel, and wherein a water transportation channelcommunicates with the cooling channel at the top end of the coolingchannel and at a top end of the water transportation channel, so thatwater, upon reaching the top of the cooling channel is gravity feddownward in the water transportation channel.
 13. An exhaust tube forconducting exhaust gases from a combustion engine, whereby the exhaustgases are cooled by means of water, wherein the exhaust tube comprisesan outer housing formed as a tube, and an inner tube extending at aradial distance from the housing, the inner tube being adapted toconduct the exhaust gases while at least one cooling channel, formedbetween the housing and the inner tube, is adapted to conduct coolingwater separately from the exhaust gases, the exhaust tube being adaptedto be mounted in a water-vessel, to extend from a first region to asecond region of the latter, the second region being located higher thanthe first region, whereby the housing delimits the at least one coolingchannel surrounding the inner tube, whereby water pump means areprovided to pump water for it to flow through the cooling channel,wherein the outlet of the exhaust tube is located above or at a top endof the cooling channel, and wherein a water transportation channelcommunicates with the cooling channel at the top end of the coolingchannel and at a top end of the water transportation channel, so thatwater can be pumped upwards in the water transportation channel andconducted downward in the cooling channel.